Free AQA GCSE Computer Science (8520) Exam Questions and Answers

Match the computer science process to each correct label. You should write a label A–F next to each process. You should not use the same label more than once. A Abstraction B Data validation C Decomposition D Efficiency E Random number generation F Variable assignment Process: 1. Breaking down a problem into sub-problems. 2. Removing unimportant details. 3. Ensuring the user enters data that is allowed, for example within a correct range.

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1. Decomposition
2. Abstraction
3. Data validation

The algorithm shown in Figure 1 is designed to help an athlete with their training. It uses two subroutines getBPM and wait: • getBPM() returns the athlete's heart rate in beats per minute from an external input device • wait(n) pauses the execution of the algorithm for n seconds, so wait(60) would pause the algorithm for 60 seconds. Line numbers have been included but are not part of the algorithm. Figure 1 1 seconds ← 0 2 rest ← 50 3 REPEAT 4 bpm ← getBPM() 5 effort ← bpm – rest 6 IF effort ≤ 30 THEN 7 OUTPUT 'faster' 8 ELSE 9 IF effort ≤ 50 THEN 10 OUTPUT 'steady' 11 ELSE 12 OUTPUT 'slower' 13 ENDIF 14 ENDIF 15 wait(60) 16 seconds ← seconds + 60 17 UNTIL seconds > 200 State the most appropriate data type of the variable seconds in the algorithm shown in Figure 1.

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The algorithm shown in Figure 1 is designed to help an athlete with their training. It uses two subroutines getBPM and wait: • getBPM() returns the athlete's heart rate in beats per minute from an external input device • wait(n) pauses the execution of the algorithm for n seconds, so wait(60) would pause the algorithm for 60 seconds. Line numbers have been included but are not part of the algorithm. Figure 1 1 seconds ← 0 2 rest ← 50 3 REPEAT 4 bpm ← getBPM() 5 effort ← bpm – rest 6 IF effort ≤ 30 THEN 7 OUTPUT 'faster' 8 ELSE 9 IF effort ≤ 50 THEN 10 OUTPUT 'steady' 11 ELSE 12 OUTPUT 'slower' 13 ENDIF 14 ENDIF 15 wait(60) 16 seconds ← seconds + 60 17 UNTIL seconds > 200 Explain why rest could have been defined as a constant in the algorithm shown in Figure 1.

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The algorithm shown in Figure 1 is designed to help an athlete with their training. It uses two subroutines getBPM and wait: • getBPM() returns the athlete's heart rate in beats per minute from an external input device • wait(n) pauses the execution of the algorithm for n seconds, so wait(60) would pause the algorithm for 60 seconds. Line numbers have been included but are not part of the algorithm. Figure 1 1 seconds ← 0 2 rest ← 50 3 REPEAT 4 bpm ← getBPM() 5 effort ← bpm – rest 6 IF effort ≤ 30 THEN 7 OUTPUT 'faster' 8 ELSE 9 IF effort ≤ 50 THEN 10 OUTPUT 'steady' 11 ELSE 12 OUTPUT 'slower' 13 ENDIF 14 ENDIF 15 wait(60) 16 seconds ← seconds + 60 17 UNTIL seconds > 200 State the line number where iteration is first used in the algorithm shown in Figure 1.

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The algorithm shown in Figure 1 is designed to help an athlete with their training. It uses two subroutines getBPM and wait: • getBPM() returns the athlete's heart rate in beats per minute from an external input device • wait(n) pauses the execution of the algorithm for n seconds, so wait(60) would pause the algorithm for 60 seconds. Line numbers have been included but are not part of the algorithm. Figure 1 1 seconds ← 0 2 rest ← 50 3 REPEAT 4 bpm ← getBPM() 5 effort ← bpm – rest 6 IF effort ≤ 30 THEN 7 OUTPUT 'faster' 8 ELSE 9 IF effort ≤ 50 THEN 10 OUTPUT 'steady' 11 ELSE 12 OUTPUT 'slower' 13 ENDIF 14 ENDIF 15 wait(60) 16 seconds ← seconds + 60 17 UNTIL seconds > 200 Complete the trace table for the algorithm shown in Figure 1. Some values have already been entered in the trace table: • the first value of seconds • the values returned by the subroutine getBPM that are assigned to the variable bpm. You may not need to use all rows of the trace table.

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A developer is writing a program to convert a sequence of integers that represent playing cards to Unicode text. The developer has identified that they need to create the subroutines shown in Figure 2 to complete the program. Figure 2 getSuit(n): Returns: the string 'hearts' if n is 0; the string 'diamonds' if n is 1; the string 'spades' if n is 2; the string 'clubs' if n is 3. getRank(n): Returns the number value of the card as a string, for example: if n is 1 then 'ace' is returned; if n is 2 then 'two' is returned; if n is 10 then 'ten' is returned; if n is 11 then 'jack' is returned. convert(cards): Returns the complete string representation of the array cards. For example: if cards is [3, 1], the string returned would be 'three of diamonds '; if cards is [1, 0, 5, 2, 7, 0], the string returned would be 'ace of hearts five of spades seven of hearts '. Explain how the developer has used the structured approach to programming.

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A developer is writing a program to convert a sequence of integers that represent playing cards to Unicode text. The developer has identified that they need to create the subroutines shown in Figure 2 to complete the program. Figure 2 getSuit(n): Returns: the string 'hearts' if n is 0; the string 'diamonds' if n is 1; the string 'spades' if n is 2; the string 'clubs' if n is 3. getRank(n): Returns the number value of the card as a string, for example: if n is 1 then 'ace' is returned; if n is 2 then 'two' is returned; if n is 10 then 'ten' is returned; if n is 11 then 'jack' is returned. convert(cards): Returns the complete string representation of the array cards. For example: if cards is [3, 1], the string returned would be 'three of diamonds '; if cards is [1, 0, 5, 2, 7, 0], the string returned would be 'ace of hearts five of spades seven of hearts '. State two benefits to the developer of using the three separate subroutines described in Figure 2 instead of writing the program without using subroutines.

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A developer is writing a program to convert a sequence of integers that represent playing cards to Unicode text. The developer has identified that they need to create the subroutines shown in Figure 2 to complete the program. Figure 2 getSuit(n): Returns: the string 'hearts' if n is 0; the string 'diamonds' if n is 1; the string 'spades' if n is 2; the string 'clubs' if n is 3. getRank(n): Returns the number value of the card as a string, for example: if n is 1 then 'ace' is returned; if n is 2 then 'two' is returned; if n is 10 then 'ten' is returned; if n is 11 then 'jack' is returned. convert(cards): Returns the complete string representation of the array cards. For example: if cards is [3, 1], the string returned would be 'three of diamonds '; if cards is [1, 0, 5, 2, 7, 0], the string returned would be 'ace of hearts five of spades seven of hearts '. Figure 3 shows the subroutine convert described in Figure 2. Some parts of the subroutine have been replaced with the labels L1 to L5. Figure 3 SUBROUTINE convert(cards) result ← '' max ← LEN(cards) index ← 0 WHILE index < L1 rank ← L2(cards[index]) suit ← getSuit(cards[L3 + 1]) c ← rank + ' of ' + suit + ' ' result ← result + L4 index ← index + 2 ENDWHILE RETURN L5 ENDSUBROUTINE State the pseudo-code that should be written in place of the labels in the subroutine written in Figure 3. L1 L2 L3 L4 L5

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A developer is writing a program to convert a sequence of integers that represent playing cards to Unicode text. The developer has identified that they need to create the subroutines shown in Figure 2 to complete the program. Figure 2 getSuit(n): Returns: the string 'hearts' if n is 0; the string 'diamonds' if n is 1; the string 'spades' if n is 2; the string 'clubs' if n is 3. getRank(n): Returns the number value of the card as a string, for example: if n is 1 then 'ace' is returned; if n is 2 then 'two' is returned; if n is 10 then 'ten' is returned; if n is 11 then 'jack' is returned. convert(cards): Returns the complete string representation of the array cards. For example: if cards is [3, 1], the string returned would be 'three of diamonds '; if cards is [1, 0, 5, 2, 7, 0], the string returned would be 'ace of hearts five of spades seven of hearts '. Shade one lozenge that states why Unicode is now commonly used in preference to ASCII.

• AA. Unicode can be represented in hexadecimal.
• BB. Unicode includes characters from many different alphabets.
• CC. Unicode is a sequential character set.
• DD. Unicode is easier to remember than ASCII.
• EE. Unicode takes up less space in memory than ASCII.

A student has written the following statements about representing images. Two are correct and two are incorrect: Statement 1 "Bitmap images are made up of pixels." Statement 2 "A 2 pixel by 4 pixel bitmap image contains 16 pixels." Statement 3 "A pixel is a single point in a graphical image." Statement 4 "Black and white images have a minimum colour depth of two." Write the correct versions of the two incorrect statements that the student has made. First corrected statement Second corrected statement

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